Code 40 custom turnout drive

MegaBlackJoe Feb 18, 2022

  1. MegaBlackJoe

    MegaBlackJoe TrainBoard Member

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    Hello fellow modellers. This day has finally come - I am extremely happy. I have finished a project that took me a few years. I have built a code 40 turnout and designed a custom drive that can switch turnout smoothly.

    Running trains that have been designed for code 55 is challenging, but possible. I am not saying every loco will run on this, but the one on the video does.

    The main goal of the project was to design a low profile drive with smooth switching and the goal has been achieved - the drive only occupies 5 mm under the ballast prism. It's quite and accurate, it can hold the position of point rails.

    You can see some of the milestones on this photo:

    prototype.jpg

    I quickly dropped some ideas like laser cut fixture, then switched to 3d printing. I spent tons of money on 3d printing services - back in the day affordable 3d printers haven't yet been available to the public. I had to print 10 parts just to understand the tolerances. I dropped the idea of 3d printed rail holders as you can't use your existing rolling stock on them. I purchased a 3d printer and then another one. And finally - I was able to do this - a fully working code 40 Z scale turnout.

    Let me know, if you would like to have one. I don't plan to produce them commercially, but if you have been looking for a drive for your handlaid turnout, I could make a couple of them for fellow Z scalers.

     
  2. CNE1899

    CNE1899 TrainBoard Member

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    Joe,
    I don't hand lay track, but this is very cool. Nice work, nice video!

    Scott
     
  3. MegaBlackJoe

    MegaBlackJoe TrainBoard Member

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    Hi, I have decided to make the design of my drive mount open source for non commercial usage. It's not perfect and it may need improvement, but if you would like to save months of tolerance tweaking, you can use my design since it has all tolerances for resin 3d printers adjusted.

    A few important things - the drive was designed for the motor that is shown on the screenshot. It's not the best choice - it's a very low torque, but it has the necessary precision and I beleive it is possible to build a turnout using this drive, you just have to make sure there is 0 resistance in moving parts - point rails need the bottom of the rail cutt off - this way you reduce the resistance (valid for code 40).

    Снимок.PNG

    Because Z scale is so small and requires more tight tolerances, this piece as you can see is not just a plain hole in the baseboard, in order to make it working, you will need to design the ballast prism for the entire turnout. I think Z scale things are possible with CAD design only and laying track manually on a corckbed will not work - at least not fot this low torque motor - the resistance shall be minimal and close to 0.

    For this reason it will not work with FastTracks in Z scale. This poorly engineered piece has wrong tie positioning not allowing to achieve accuracy which is crucial for Z scale. So you may want to CNC cut PCB ties - there should be at least 2 PCB ties (4 ties as a single block) on each end of the rail to fix the ends in the same height. Something that FastTracks doesn't allow you to do with thier faulty turnout jig. Even the slightest warps in height will prevent the motor from spinning. Fasttracks throwbar is ridiculously thin - the one I am using is also custom to be able to hold an M 1.3 screw (European standart).

    A few words about printing - the best way to print this is to position the parts straight on the plate without supports - this way you won't have to delete supports with a file. This is especially crucial for the moving part (designed to hold an M 1.3 nut). If there are too many supports on this part, you will ruin the tolerances - it will become too loose. It's better to print it on the platform directly. If you are not using bottom layer elephant foot compensation, it shall work fine anyway - elephant foot is easier to remove than individual bumps from supports.

    For the driver you can use a simple arduino and there is a sketch sample which already there - by adjusting the number of rotations you are adjusting the distance of throwbar travel.

    Enjoy.
     

    Attached Files:

  4. HoboTim

    HoboTim TrainBoard Supporter

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    Do you have any photos of your turnout being built? This is awesome!!!
     
  5. rray

    rray Staff Member

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    Yes please! A photo how to would be awesome!
     
    HoboTim likes this.
  6. MegaBlackJoe

    MegaBlackJoe TrainBoard Member

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    Sorry, guys. I have no photos. But on the video thumbnail you can pretty much see the essential elements of the turnout - the ballast prism is 3d printed in pieces. I am using a flexible resin (local brand not available in the US as far as I know) - this helps to reduce the noise and because it's a high quality resin - it has a very low shrinkage rate that has almost 0 warping of parts). With cheap chinese resins you probably wont be able to print the parts as they get warped.

    I wish I could avoid 3d printing the ballast prism, but in the prototypes with the cork one I found out that the vertical alignment of rails is crucial for Z scale turnouts and this stepper motor in particular. The cork is very soft - it causes some bending and the edges are far from being perfect with the varying height.

    cork.jpg


    So I had to 3d print the ballast prism, it turned out to be more rigid and dimensionally accurate. I printed it in pieces. I also discovered that the although the parts are more dimensionally accurate, there is still a slight height variance that required some new measures to align the rails vertically lol. So I had to design my own PCB ties for that. On the video thumbnail you can see a single block of 4 PCB ties that are glued to the ballast prism where different pieces of ballast prism join together (to compensate for this height difference). 2 PCB ties for each rail end to make sure the alignment is perfect.

    Next I designed the wooden ties in CAD program. I wanted to have wooden ties as I stain them and it gives a nice look, but it's easier to 3d print them together with the ballast prism. Commercially available wooden ties are not suitable here - fasttracks ties need a lot of filing. Kappler ties are better, but we still have ties with varying height that needs sanding and it's very time consuming to lay each tie individually. So i took a very thin sheet of plywood and laser cut them in small blocks and just glued them in place.

    Next I simply started soldering the rails. The process with some important steps is shown in fasttracks videos. I am using 2 fasttracks tools that I find usefull - stock and frog rail filing jigs that help to file off the rails under the right angle (not perfect but better than nothing, you can also build your own one if you have a belt sander, I don't so I am using the jigs). But their turnout building jig is just a joke - it has wrong PCB tie placement and can't be used for Z scale. On the video you can see that I also desined a separate PCB block for the frog area. Soldering rails is a bit tricky - you have to use a powerfull iron and a good flux (this is the key in this process as well) and at the same time avoid melting the prism. 4 MTL coupler gauge tools will help to hold the rails in palce at the right distance while you are soldering them. Small amounts of solder has to be added to avoid solder bulbs.

    This photo shows fasttracks failure on the bottom and my own turnout at the top. I could not achieve any results with fasttracks turnout jig - see my previous posts for details. The idea of gluing the ready made Fast Tracks piece didn't work - at least not for Z scale. Individual wooden ties for fasttracks didn't work either.

    The ballast looks terrible as I tried a new technique which didn't quite work, now it improved a lot.

    fasttracksBS.jpg

    The throwbar is a custom PCB tie as well it has a hole for the M 1.3 screw that connects the pcb tie and the 3dprinted part which is then moved by the steppper motor. You have to cut the hole in the baseboard for the stepper motor. Since I am a fan of CAD and accuracy, I did laser cutting. But the profile of this square hole is simple and you can use any available tools to do it.

    Let me know if you have any further questions.
     

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